A NullPointerException is thrown in DBTCPConnector.close() due to _rsStatus being null when _rsStatus.close() is called.

If you call the constructor

public Mongo( ServerAddress addr , MongoOptions options )

then, the constructor is called:

public DBTCPConnector( Mongo m , ServerAddress addr )

if the ServerAddress is not paired, then the following code sets _rsStatus to null:

if ( addr.isPaired() )

{ _allHosts = new ArrayList<ServerAddress>( addr.explode() ); _rsStatus = new ReplicaSetStatus( m , _allHosts ); _createLogger.info( "switching to replica set mode : " + _allHosts + " -> " + _curMaster ); }

else

{ _set( addr ); _allHosts = null; _rsStatus = null; }

when DBTCPConnector.close() is eventually called, _rsStatus.close() throws an NPE.

Although _portHolder should never be null, I think it is worth checking it before calling close() on it, as well.

I'll submit a pull request from my fork at http://github.com/RobertStewart/mongo-java-driver.